diff options
| author | Waiman Long <longman@redhat.com> | 2022-06-14 18:03:59 -0400 |
|---|---|---|
| committer | akpm <akpm@linux-foundation.org> | 2022-06-16 19:48:32 -0700 |
| commit | 6edda04ccc7cfb281d139e352dbd5dd933bd2751 (patch) | |
| tree | b2636bc590cb869ec6ad0ff59daabf2693b8bdc6 /mm/kmemleak.c | |
| parent | 64977918c2381aaadd544535708294213cc964f6 (diff) | |
mm/kmemleak: prevent soft lockup in first object iteration loop of kmemleak_scan()
The first RCU-based object iteration loop has to modify the object count.
So we cannot skip taking the object lock.
One way to avoid soft lockup is to insert occasional cond_resched() call
into the loop. This cannot be done while holding the RCU read lock which
is to protect objects from being freed. However, taking a reference to
the object will prevent it from being freed. We can then do a
cond_resched() call after every 64k objects safely.
Link: https://lkml.kernel.org/r/20220614220359.59282-4-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/kmemleak.c')
| -rw-r--r-- | mm/kmemleak.c | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 30d9bd41e5a1..1eddc0132f7f 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -1474,12 +1474,16 @@ static void kmemleak_scan(void) struct zone *zone; int __maybe_unused i; int new_leaks = 0; + int loop1_cnt = 0; jiffies_last_scan = jiffies; /* prepare the kmemleak_object's */ rcu_read_lock(); list_for_each_entry_rcu(object, &object_list, object_list) { + bool obj_pinned = false; + + loop1_cnt++; raw_spin_lock_irq(&object->lock); #ifdef DEBUG /* @@ -1505,10 +1509,32 @@ static void kmemleak_scan(void) /* reset the reference count (whiten the object) */ object->count = 0; - if (color_gray(object) && get_object(object)) + if (color_gray(object) && get_object(object)) { list_add_tail(&object->gray_list, &gray_list); + obj_pinned = true; + } raw_spin_unlock_irq(&object->lock); + + /* + * Do a cond_resched() to avoid soft lockup every 64k objects. + * Make sure a reference has been taken so that the object + * won't go away without RCU read lock. + */ + if (!(loop1_cnt & 0xffff)) { + if (!obj_pinned && !get_object(object)) { + /* Try the next object instead */ + loop1_cnt--; + continue; + } + + rcu_read_unlock(); + cond_resched(); + rcu_read_lock(); + + if (!obj_pinned) + put_object(object); + } } rcu_read_unlock(); |